<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>vw适配</title>

    <style>
        * {
            margin: 0;
            padding: 0
        }

        #demo {
            width: 92vw;
            height: 40vw;
            background-color: skyblue;
            margin: 0 auto;
            margin-top: 4vw;
        }
    </style>
</head>

<body>
    <div id="demo"></div>
</body>

</html>